1. Field of the Invention
The present invention relates to an ink jet head for effecting recording by discharging ink, a substrate for such a head, methods for manufacturing the head and the substrate, a method for using such a head and an ink jet recording apparatus.
2. Related Background Art
An ink jet recording system disclosed in U.S. Pat. No. 4,723,129 or U.S. Pat. No. 4,740,796 can effect recording at a high speed with high accuracy and high image quality and is suitable for color recording and compactness. In a recording head using such an ink jet recording system and adapted to discharge ink onto a recording medium by bubbling the ink by means of thermal energy, heat generating resistance members for bubbling the ink and wirings for electrical connection thereto are formed on the same substrate to provide an ink jet recording head substrate, and nozzles for discharging the ink are generally formed on the substrate.
The ink jet recording head substrate has widely been devised in order to save electrical energy and to prevent reduction of a service life of the substrate due to mechanical damage caused by bubbling and destruction of a heat generating portion caused by thermal pulse. Particularly, many investigations have been made regarding a protection film for protecting a heat generating resistance member having a heat generating portion positioned between a pair of wiring patterns from ink.
In the viewpoint of heat efficiency, the protection film is advantageous to have high heat conductivity or smaller thickness. However, on the other hand, the protection film has the purpose for protecting the wirings connected to the heat generating member from the ink, and the film is advantageous to have greater thickness in consideration of probability of defect of the film, and an optimum thickness of the film is set in the viewpoint of energy efficiency and reliability. However, the protection film is subjected to both cavitation damage, i.e., mechanical damage due to the bubbling of ink and damage due to chemical reaction with high temperature ink component since a temperature of the surface of the film is increased after the bubbling.
Thus, in actual, it is difficult to make an insulation film for protecting the wirings and a film having stability with respect to mechanical and chemical damages compatible, and, for this reason, the protection film of the ink jet substrate is generally constituted by an upper layer having high stability with respect to mechanical and chemical damages due to the ink bubbling and a lower layer insulation layer for protecting the wirings. More specifically, a Ta film having very high mechanical and chemical stability is generally used as the upper layer, and an SiN film or an SiO film which can be formed easily and stably by an existing semiconductor device is generally used as the lower layer.
Explaining in more detail, an SiN film having a thickness of about 0.2 to 1 xcexcm is formed as a protection film on the wirings, and then, an upper layer protection film, i.e., a Ta film having a thickness of 0.2 to 0.5 xcexcm called as an anti-cavitation film having a function for resisting to cavitation is formed. With this arrangement, both the service life and reliability of the heat generating resistance member of the ink jet substrate can be enhanced.
Further, other than the mechanical and chemical damages, in the heat generating portion, coloring material and additives included in the ink are decomposed to a molecular level by high temperature heating to be changed into substance hard to solve, which is physically adhered to the anti-cavitation film as the upper layer protection film. This phenomenon is called as xe2x80x9ckogation.xe2x80x9d As such, if organic or inorganic substance hard to solve is adhered to the anti-cavitation film, heat transfer from the heat generating resistance member to the ink becomes uneven, thereby making the bubbling unstable. In order to avoid this, although it is required that the kogation does not occur on the anti-cavitation film, the above-mentioned Ta film is generally adopted as a film having relatively good kogation resistance.
By the way, recently, as the performance of the ink jet printer has remarkably been enhanced, enhancement of performance of ink, for example, prevention of bleeding (smudge between different color inks) in correspondence to high speed recording has been requested, and enhancement coloring ability and weather resistance ability in correspondence to high image quality has been requested. To this end, various components are added to the ink, and, different components are added to three colors, i.e., yellow (Y), magenta (M) and cyan (C), which are kinds of inks for forming a color image.
As a result, for example, in an ink jet head in which heat generating portions for three colors (Y), (M), (C) and a Ta film, as the upper layer protection layer, are formed on the same substrate, from the difference between the ink components, in the heat generating portion corresponding to a certain color, the Ta film, which was regarded as stable film up to now, may also be eroded, with the result that the lower layer protection film and the heat generating member are also damaged to destroy the substrate. For example, when ink including bivalent metal salt such as Ca or Mg or component forming chelate body is used, the Ta film is apt to be eroded by thermal chemical reaction with ink.
On the other hand, other anti-cavitation films have been developed in correspondence to improvement of ink components. For example, in place of the Ta film, when amorphous alloy including Ta disclosed in Japanese Patent No. 2,683,350 according to the Applicant is used, even if the ink includes high erosive ink component, it was found that damage does almost not occur.
Thus, it can be considered that the amorphous alloy including Ta is used as the upper layer protection film for the heat generating portion in the ink jet head capable of discharging three color (Y, M, C) inks. However, although the amorphous alloy including Ta has high ink erosion resistance, since the surface of alloy is almost not subjected to damage, there is the tendency that kogation is apt to occur.
Thus, in the heat generating portion corresponding to a certain color, in place of the fact that the upper layer protection film is almost not eroded, a problem regarding kogation arises. In addition, when ink having high kogation ability in the different color ink is used, in the conventional Ta, although there was no problem regarding the kogation, when changed to the amorphous alloy including Ta, kogation will become noticeable. Incidentally, in the conventional Ta, the reason why the kogation does almost not occur is that slight erosion of Ta film and kogation occurs in a good balanced condition, with the result that accumulative generation of the kogation can be suppressed by the gradual erosion removal of the surface of the Ta film.
As mentioned above, in the arrangement in which either the Ta film or the amorphous alloy including Ta is used as the upper layer protection film contacted with the ink, it is difficult to make the service life and reliability of the ink jet head, separately, using ink having high kogation ability and high erosive ink on the same substrate well compatible.
In consideration of the above, an object of the present invention is to provide an ink jet head substrate capable of using both ink having high kogation ability and high erosive ink, an ink jet head utilizing such a substrate, and an ink jet recording apparatus having such a head.
Another object of the present invention is to provide an ink jet head substrate having a new intervention layer (or film) capable of removing factors for generating kogation and having no reduction of discharging speed in comparison with a conventional Ta protection film or a new anti-cavitation function capable of being contacted with liquid from an initial condition, an ink jet head utilizing such a substrate, a method for manufacturing such a substrate, and a method for using such a head.
A further object of the present invention is to provide a head capable of maintaining a property more positively in a head (for example, refer to Japanese Patent Application Laid-Open No. 2000-62180) including a movable member shifted by generation of a bubble and having an anti-cavitation layer providing a good discharging property. Particularly, although the head having the movable member has an advantage that higher frequency driving (than conventional one) can be effected, this property causes abrupt generation of the bubble with high frequency period and has a tendency that high level is requested to a bubble generating area. The present invention provides a new head substrate not only maintaining the advantage of such a head but also avoiding an influence affecting upon the anti-cavitation layer due to property (reactivity and/or high pH) of ink used.
To achieve the above object, the present invention provides an ink jet head substrate having a heat generating resistance member forming a heat generating portion, an electrode wiring electrically connected to the heat generating resistance member, and an anti-cavitation film provided on the heat generating resistance member and the electrode wiring via an insulation protection layer, and wherein the anti-cavitation film is formed from different materials more than two layers.
Further, the present invention provides an ink jet head substrate having a heat generating resistance member forming a heat generating portion, an electrode wiring electrically connected to the heat generating resistance member, and an anti-cavitation film provided on the heat generating resistance member and the electrode wiring via an insulation protection layer, and wherein the anti-cavitation film is formed from at least two layer films, and an upper layer film contacted with ink has lower ink erosion resistance than a lower layer film.
Further, the present invention provides an ink jet head substrate having a heat generating resistance member forming a heat generating portion, an electrode wiring electrically connected to the heat generating resistance member, and an anti-cavitation film provided on the heat generating resistance member and the electrode wiring via an insulation protection layer, and wherein the anti-cavitation film is formed from at least two layer films, and an upper layer film contacted with ink is a film on which kogation is relatively hard to occur, and a lower layer film is a film having high ink erosion resistance.
More specifically, in the anti-cavitation film, the upper layer film contacted with ink is a Ta film or a TaAl film, and the lower layer film is an amorphous alloy film including Ta.
The amorphous alloy film has a composition comprised of Ta, Fe, Ni and Cr is preferably represented as follows:
Taxcex1Fexcex2Nixcex3Crxcex4xe2x80x83xe2x80x83(I)
(However, 10 at. %xe2x89xa6xcex1xe2x89xa630 at. % and xcex1+xcex2 less than 80 at. % and xcex1 less than xcex2 and xcex4 greater than xcex3 and xcex1+xcex2+xcex3+xcex4=100 at. %).
Particularly, it is preferable that the anti-cavitation film has a first layer represented by the formula (I):
Taxcex1Fexcex2Nixcex3Crxcex4xe2x80x83xe2x80x83(I)
(However, 10 at. %xe2x89xa6xcex1xe2x89xa630 at. % and xcex1+xcex2 less than 80 at. % and a less than xcex2 and xcex4 greater than xcex3 and xcex1+xcex2+xcex3+xcex4=100 at. %), and a second layer made of Ta and comprising a square grating crystal structure formed on the first layer.
Further, the present invention includes an ink jet head in which a liquid path communicated with a discharge port for discharging ink droplets is provided in correspondence to the heat generating portion on the above-mentioned ink jet head substrate. Particularly, in the ink jet head to which the head substrate of the present invention is applied, it is preferable that a plurality of flow paths communicated with the discharge ports are provided, and different inks are supplied to the respective flow paths. In this case, the different inks are at least ink apt to incur kogation and ink having high erosion ability.
Further, the present invention provides a method for manufacturing an ink jet head substrate having a heat generating resistance member forming a heat generating portion, an electrode wiring electrically connected to the heat generating resistance member, and an anti-cavitation film provided on the heat generating resistance member and the electrode wiring via an insulation protection layer, and wherein, in order to form the anti-cavitation film, a Ta film having a square grating crystal structure is formed on a layer having composition comprised of Ta, Fe, Ni and Cr by sputtering using a metal Ta target having purity of 99% or more. The layer having composition comprised of Ta, Fe, Ni and Cr is preferably represented as follows:
Taxcex1Fexcex2Nixcex3Crxcex4xe2x80x83xe2x80x83(I)
(However, 10 at. %xe2x89xa6xcex1xe2x89xa630 at. % and xcex1+xcex2 less than 80 at. % and xcex1 less than xcex2 and xcex4 greater than xcex3 and xcex1+xcex2+xcex3+xcex4=100 at. %).
An ink jet head in which a liquid path communicated with a discharge portion for discharging ink droplets is provided in correspondence to the heat generating portion on the ink jet head substrate manufactured by such a manufacturing method is also included in the present invention.
In this case, in the ink jet head, it is preferable that the anti-cavitation film has initially two layers, and a stage in which the discharging is effected while partially removing an upper layer Ta and a stage in which the discharging is effected while removing the Ta only in an effective bubbling area can be performed.
Further, the present invention provides a method for manufacturing an ink jet head in which a liquid path communicated with a discharge port for discharging ink droplets is provided in correspondence to the heat generating portion on the ink jet head substrate having a heat generating resistance member forming a heat generating portion, an electrode wiring electrically connected to the heat generating resistance member, and an anti-cavitation film provided on the heat generating resistance member and the electrode wiring via an insulation protection layer, and wherein, in order to form the anti-cavitation film, a Ta film having a square grating crystal structure is formed on a layer having composition comprised of Ta, Fe, Ni and Cr by sputtering using a metal Ta target having purity of 99% or more. The layer having composition comprised of Ta, Fe, Ni and Cr is preferably represented as follows:
Taxcex1Fexcex2Nixcex3Crxcex4xe2x80x83xe2x80x83(I)
(However, 10 at. %xe2x89xa6xcex1xe2x89xa630 at. % and xcex1+xcex2 less than 80 at. % and xcex1 less than xcex2 and xcex4 greater than xcex3 and xcex1+xcex2+xcex3+xcex4=100 at. %).
In this manufacturing method, after the flow path is formed, by performing a preliminary ink discharging operation, it is preferable that Ta is substantially doped to an amorphous immobile layer including at least Ta and Cr of the Taxcex1Fexcex2Nixcex3Crxcex4 layer.
Further, a method for using the ink jet head manufactured by this manufacturing method, wherein the layer obtained by substantially doping Ta into the amorphous immobile layer including at least Ta and Cr of the Taxcex1Fexcex2Nixcex3Crxcex4 layer is used as a first surface for the ink or as a layer exposed later, or wherein the layer obtained by adding Ta into the amorphous surface layer including at least Ta and Cr of the Taxcex1Fexcex2Nixcex3Crxcex4 layer is used as a first surface for the ink or as a layer exposed later is also included in the present invention.
Further, the present invention can preferably be applied to the above-mentioned ink jet head in which a movable member having a free end displaced by growth of a bubble generated in the liquid by thermal energy from the heat generating portion is positioned in each flow path.
Further, the present invention, also includes an ink jet recording apparatus having a carriage on which the above-mentioned ink jet head is mounted and effecting recording on a recording medium by discharging the ink droplet from the ink jet head while shifting the carriage in response to recording information.